U.S. Pat. No. 4,756,291 discloses a pressure control for the fuel system of an internal combustion engine. The known system has a pressure sensor in a fuel line between an electric fuel pump and a carburetor. The pressure sensor supplies to electrical control circuitry a signal representing the sensed pressure. The electrical control circuitry in turn controls the electrical power to the pump such that the fuel pressure delivered to the carburetor is closed-loop regulated to a commanded pressure. The commanded pressure may be established by an engine management computer, and is subject to being varied in accordance with engine operating conditions. The disclosure of U.S. Pat. No. 4,756,291 is directed toward elimination of a fuel return line from the engine for returning excess pumped fuel to the fuel tank.
Certain U.S. patents relate to electronic multi-point fuel injection systems. Typically, such a system comprises a fuel rail assembly that contains several electrically operated fuel injectors and a mechanical fuel pressure regulator. Fuel is pumped into the fuel rail assembly at a rate exceeding the maximum engine demand. The fuel pressure regulator regulates the pumped fuel pressure, returning excess fuel to the tank via a return line. The typical pressure regulator comprises a housing divided by a movable wall into a fuel pressure chamber that is communicated to the fuel in the fuel rail assembly and a chamber that is communicated to intake manifold vacuum. The movable wall carries a valve element that co-acts with an internal seat in the fuel pressure chamber to control the return fuel flow such that the pressure in the fuel rail is thereby regulated to a pressure that is pressure-compensated with respect to changes in intake manifold pressure whereby the pressure across each fuel injector is held substantially constant despite variations in the intake manifold pressure. In the typical naturally aspirated engine, the intake manifold pressure is sub-atmospheric, ranging from relatively high vacuum at light loads to relatively low vacuum at high loads. With a substantially constant pressure drop across a fuel injector, the amount of fuel injected by the injector for each injection is a function of the electrical pulse width energization of the injector applied by an associated engine management computer.
If it is attempted to embody an electronic fuel injection fuel system, such as one of those of the patents referred to in the immediately preceding paragraph, with a pump whose output pressure is electrically controlled in the manner of the first-mentioned patent above, the failure to take the intake manifold pressure into account will introduce error into the fuel injections whenever the intake manifold pressure varies from a particular set-point. The use of pressure regulators such as those just described will obviously be unacceptable since a return line is required, and the disclosure of the first-mentioned patent apparently does not appear to address any question of intake manifold pressure, possibly because of the fact that it uses a carburetor.
The present invention relates to a new and unique internal combustion engine fuel system in which the electric power delivered to an electrically powered fuel pump is controlled by means of closed-loop feedback which derives a feedback signal from a pressure sensor that takes intake manifold pressure variations into account. As a result, the pump output pressure is closed-loop regulated to commanded pressure despite the variations in intake manifold pressure that typically occur during engine operation.
The invention includes the advantages of: embodying the fuel pressure sensing and intake manifold pressure sensing functions in a single device; eliminating any need to interface with a separate MAP (manifold absolute pressure) sensor; and possible savings in wiring and circuitry. Further features, advantages, and benefits of the invention will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.